添加硼对La-Mg-Ni系(PuNi3-型)贮氢合金微观结构及电化学性能的影响

为了提出La-Mg-Ni(PuNi3型)系贮氢合金的电化学循环稳定性,在La2Mg(Ni0.85Co0.15)9合金中添加微量的B,用铸造及快淬工艺制备La2Mg(Ni0.85Co0.15)9Bx(x=0,0.05,0.10,0.15,0.20)贮氢合金,分析测试铸态及快淬态合金的微观结构与电化学性能,研究硼对合金微观结构及电化学性能的影响。结果表明:铸态合金具有多相结构,包括主相(La,Mg)Ni3相(PuNi3型)和LaNi5相,一定量的LaNi2相和微量的Ni2B相经快淬处理后,Ni2B相消失,且其他相的相对量随淬速的变化而变化。硼的加入提高了铸态及快淬态合金的循环稳定性,但使铸态合金的容量下降;铸态合金的电化学容量随B含量的增加单调下降,而快淬态合金的容量随B含量的增加有一极大值,B对铸态及快淬态合金电化学性能的影响机理是完全不同的。

Effects of boron additive on microstructures and electrochemical performances of La-Mg-Ni system (PuNi3-type) hydrogen storage alloy

In order to improve the electrochemical cycle stability of La-Mg-Ni system(PuNi3-type) hydrogen storage alloy,B was added to La2Mg(Ni0.85Co0.15)9 alloy.La2Mg(Ni0.85Co0.15)9Bx(x = 0,0.05,0.10,0.15,0.20) hydrogen storage alloys were prepared by casting and rapid quenching.The microstructures and electrochemical performances of the as-cast and quenched alloys were analyzed and measured.The effects of B additive on the microstructures and electrochemical performances of as-cast and quenched alloys were investigated.The results show that the as-cast and quenched alloys are composed of the(La,Mg)Ni3 phase(PuNi3 structure),LaNi5 phase and LaNi2 phase,Ni2B phase exists in the as-cast alloys containing B.The Ni2B phase in the alloys containing B nearly disappears after rapid quenching,and the relative amount of each phase in the alloys changes with the variety of the quenching rate.The addition of B markedly enhances the cycle stabilities of the as-cast and quenched alloys,but obviously decreases the capacity of the alloys.With the increase of the quenching rate,the capacity of the as-cast alloy decreases monotonously,whereas the capacity of the as-quenched alloy has a maximum value.The activation behaviour of B additive on the electrochemical performances of the as-cast and quenched alloys is completely different.